For the Ginger-Agave Syrup : In a resealable jar, stir ginger juice into a gave nector until loosened, cover and shake well. Store for upto 1 week, shake before using.

For the Cocktail : Combine lemon juice, Ginger-Agave Syrup and tequila in a cocktail shaker. Fill shaker with ice and shake until well chilled, about 15 seconds.

Strain into a double rock galss over a large ice cube. Top with mezcal and serve.